How to byte-swap a 32-bit integer in python?

python integer endianness
Patrick B. picture Patrick B. · Dec 16, 2014 · Viewed 40.2k times · Source

Take this example:

i = 0x12345678
print("{:08x}".format(i))
   # shows 12345678
i = swap32(i)
print("{:08x}".format(i))
   # should print 78563412

What would be the swap32-function()? Is there a way to byte-swap an int in python, ideally with built-in tools?

Answer

Carsten picture Carsten · Dec 16, 2014

One method is to use the struct module:

def swap32(i):
    return struct.unpack("<I", struct.pack(">I", i))[0]

First you pack your integer into a binary format using one endianness, then you unpack it using the other (it doesn't even matter which combination you use, since all you want to do is swap endianness).

Related questions

Endianness of integers in Python

I'm working on a program where I store some data in an integer and process it bitwise. For example, I might receive the number 48, which I will process bit-by-bit. In general the endianness of integers depends on the machine representation …

Read More
How do I parse a string to a float or int?

In Python, how can I parse a numeric string like "545.2222" to its corresponding float value, 545.2222? Or parse the string "31" to an integer, 31? I just want to know how to parse a float str to a float, and (separately) an int …

Read More
Converting integer to string in Python

I want to convert an integer to a string in Python. I am typecasting it in vain: d = 15 d.str() When I try to convert it to string, it's showing an error like int doesn't have any attribute called str.

Read More